1. Field of the Invention
The present invention relates to an optical element.
2. Description of the Related Art
An optical element 10 that adjusts a quantity of transmitted light by using electrocapillarity (electrowetting phenomenon) has been suggested (see JP-A-2001-228307).
As shown in FIG. 13, the optical element 10 includes an airtight container 16 that has end face walls 12 opposite to each other in a thicknesswise direction, and side walls 14 connecting the end face walls 12, a first liquid 20 that is sealed in the container 16 and has polarity or conductivity, and a second liquid 22 that is sealed in the container 16 and has larger transmittance than the first liquid 20.
In addition, as the first liquid 20 and the second liquid 22, liquids having properties that are not mixed with each other, and liquids that have the same specific gradient are used. In a case in which only the first liquid 20 and the second liquid 22 are sealed in the container 16 without air permeating into the container 16, even though the container 16 is made to rotate or the container 16 is shaken, the initial state in which only the first liquid 20 and the second liquid 22 are sealed in the container 16 is maintained, and a state in which the interface 24 is substantially parallel to the end face wall 12 is maintained.
In FIG. 13, reference numeral 28 indicates an electrode for applying a voltage to the first liquid 20, and reference numeral 30 indicates an insulating film to cover the electrode 28.
In addition, when the voltage is applied to the first liquid 20 by the voltage applying means, by electrocapillarity, the interface 24 between the first liquid 20 and the second liquid 22 deforms, as shown by solid lines and broken lines of FIG. 13, and thus a transmitting path 18 of light that passes through the end face wall 12 and propagates in a thicknesswise direction in the container 16 is formed.
Specifically, in a state in which a voltage is not applied, as shown by solid lines in FIG. 13, the first liquid 20 extends over the entire region in a direction orthogonal to a light transmitting direction, which results in obstructing light transmission or reducing a quantity of transmitted light. At this time, if an applied voltage is increased, as shown by broken lines in FIG. 13, the second liquid 22 comes into contact with the two end face walls 12 to form a transmitting path 18. By adjusting an applied voltage, a contact area between the second liquid 22 and one end face wall 12 is increased or decreased, and thus the size of the transmitting path 18 is adjusted.
Meanwhile, when the optical element 10 is mounted on an imaging device, such as a digital camera, it is required for the imaging device to be small-sized, and it is required to reduce the size of the optical element 10 in a thicknesswise direction (light transmitting direction).
Accordingly, there is a need for an optical element capable of achieving a small size.